This invention relates to a process utilizing novel catalysts for the conversion of biomass to useful gaseous and liquid organic products. More specifically, the invention relates to a process whereby biomass is converted substantially to useful gaseous and liquid organic products in the presence of ruthenium-bearing catalysts.
An awareness of the limitations of petroleum reserves has caused an increased interest in finding alternative energy sources. Renewable energy sources, such as crops which can be grown and processed to supply chemical and energy demands, are particularly attractive. Chemical and energy yields vary from crop to crop depending on the chemical constituency of each plant. Compositions vary from wood which is about all lignocellulosic to some perennial crops, such as milkweed (asclepias), which naturally contain up to about 43 weight percent based on the total weight of the plant of useful recoverable organic compounds. Other plant sources in which useful recoverable organic compounds comprise a portion of their compositions include, but are not limited to, plants belonging to the families of Euphorbiaceae, Moraceae, Apocynaceae, Asclepiadaceae and Compositae. Specific genera that contain recoverable hydrocarbons as a portion of their compositions include Hevaea, Manihot, Mabea, Sabium, Ricinus, Asclepias (milkweed), Solidago (goldenrod) and Euphorbia. E. lathrus (gopher plant) and E. tirucalli (aveloz, milk bush) are also plants that generate hydrocarbon constituents. Other examples include E. resinifera, E. trigona, E. cerifera (candelilla) and Parthenium argentatum (guayule).
Generally, three classes of products are obtained from the thermochemical conversion of biomass: gaseous products such as carbon dioxide, hydrogen, methane, and other light hydrocarbons; liquid organic compounds which are usually water-soluble as well as soluble in an organic solvent like acetone, methyl ethyl ketone and alcohols, such as alcohols, ketones and phenols, referred to hereinafter as liquid organic products; and a solid or near solid product which comprises tar/oils and char.
Heavy tar/oils are the chief product of most thermochemical conversions of biomass. Such tar/oils are usually solid or near solid at room temperature and difficult to handle and utilize. These tar/oils are used principally as second-grade fuel material and are valued on the basis of their heating values, measured in BTU/lb. Tar/oils typically have heating values in the range of from about 10,000 BTU/lb to about 16,000 BTU/lb.
The gaseous and liquid products from the thermoconversion reaction of biomass may be used directly as heating fuels or have other direct applications or be used as intermediates for the synthesis of other chemicals. Much attention in the field of thermochemical conversion of biomass has been directed toward the decreased production of solid and semisolid tar/oils and the increased production of gaseous and liquid organic products, predominantly gaseous and liquid hydrocarbons. U.S. Pat. No 2,551,579 to Berl discloses a process for the production of liquid or semiliquid organic compounds from plant material. Berl's process comprises heating plant matter containing carbohydrates and lignin in a closed system to a temperature between 150.degree. C. and 370.degree. C. in the presence of water and an alkaline-reacting ammonium compound such as ammonium sulfide or ammonium hydrosulfide.
U.S. Pat. No 3,505,204 to Hoffman describes a process for the direct conversion of carbonaceous material to hydrocarbons. This is a catalytic conversion of materials such as coal to oxygen-containing organic materials such as alcohols aldehydes, ketones, and acids. The catalyst is a two-component system comprising an alkali metal or alkaline earth metal compound and a Group VIII transition metal oxide. The carbonaceous material, steam and catalyst are reacted at a temperature between about 220.degree. F. and 280.degree. F. The handling, processing, and products obtained from biomass conversion are quite different from those obtained from the conversion of coal. Thus, the process disclosed by Hoffman would not be considered directly applicable to biomass conversion nor would any hydrogenation catalysts be expected to perform similarly when contacted with coal products and biomass material.
What is lacking in the field of thermochemical biomass conversion is a process which converts biomass into useful materials substantially other than tar/oils.
Therefore, it is one object of this invention to provide a process for the direct thermochemical conversion of biomass to predominantly gaseous and liquid organic products.
It is another object of this invention to provide a novel catalyst for the selective conversion of biomass to gaseous and liquid organic compounds.
These and other objects of the invention, together with the advantages thereof, will become apparent from the following specification and appended claims: